Method and apparatus for selective preheating of solid phase pressure formed web or sheet material

ABSTRACT

Mold insert apparatus and a method is provided for high pressure solid phase forming of relatively thin web or sheet material. The apparatus includes a die set assembly provided with a forming die set unit having a die forming cavity which receives a forming die and an opposed high pressure chamber die set unit wherein the die set units receive material to be formed therebetween when in spaced relationship and functional to clamp the material therebetween when the die set units are in closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the high pressure chamber die set unit. A material preheating station is provided outside but generally proximal to the die forming cavity of the forming die set unit. The preheating station includes a pair of duck-bill shaped preheating devices, with one of the devices being connected to the high pressure chamber die set unit for movement therewith while the other preheating device is connected to a stripper frame which is a part of the forming die set unit. The preheating devices open and close with the high pressure chamber die set unit and forming die set unit of the die set assembly so that preheating of web or sheet material is synchronized with forming of previously preheated material in the die set assembly. The preheating devices are provided with opposed heat insulating zones of predetermined shape which prevents the portion of material in general alignment with the insulating zones from being heated as high a temperature as material out of alignment with insulating zones. The heat insulating zones of the preheating devices are configured to conform to high force producing areas of the forming die. Selective preheating of the web or sheet before forming thus minimizes thinning of the material over the high force inducing areas of the forming die.

RELATED APPLICATION

[0001] This is a non-provisional application and claims priority in part on Provisional Application Serial No. 60/276,356, filed Mar. 16, 2001, and entitled Solid Phase Pressure Forming Tool Set and Method of Solid Phase Pressure Forming.

BACKGROUND

[0002] 1. Field of the Invention

[0003] This invention relates generally to improved film insert forming equipment apparatus and a method for selective preheating of high pressure, solid phase formed relatively thin sheets or webs of various materials that are to be formed by deep drawing. The invention particularly concerns selective preheating of synthetic resin film insert material or other thin materials that are to be deep drawn and that have been premarked with surface decoration for image information. Deep drawn plastic products having surface decoration or image information have particular utility for use in fabrication of products generally referred to in the trade as “in-mold” or “insert mold” decorating (IMD). In conventional “in-mold” film insert processes, a plastic film decorated with a preprinted image and/or printed characters is normally inserted in the injection mold cavity with the film positioned against the mold surface and the image or characters on the film facing inwardly so that the printing is visible but fully protected by the layer of film in the final molded product.

[0004] The preheating apparatus and process of this invention is useful for processing various IMD film insert synthetic resin materials, laminated materials, including metals and laminated metals, including those that have been coated with a decorative design or printed information, either in the form of, for example, an ink film applied by conventional printing or screen printing, vacuum-evaporated metallic thin film, or similar materials, including electrically conductive varnish film, or similar layers.

[0005] Deep drawing of material including film insert image or other printed information is facilitated by preheating of the web or sheet material to a level preferably below its glass transition stage temperature (T_(G)). A relatively high isostatic fluid pressure is then applied to the softened material to deform the material and in many instances the image section into a relatively deep die cavity.

[0006] An important advantage of this invention is that the apparatus incorporates and is especially adapted to permit utilization of hydraulically actuated components that have long been used in sheet-fed die and platen press equipment conventionally employed for die cutting and stamping. A master forming die assembly is positioned at a material forming station between the ram actuator of the press and a floating bolster support for the die set assembly. Preheating of the material to a level below its T_(G) temperature prior to forming requires controlled handling of the material so that the image section of the relatively thin material is precisely aligned with the forming die member of the separable die set assembly.

[0007] The apparatus and process hereof therefore includes mechanism for assuring precise alignment of each of the preheated design or image-bearing sections of the web or sheet material with the deep-draw die set, and to accomplish such alignment at a reasonably rapid rate.

[0008] 2. Description of the Prior Art

[0009] Niebling, Jr. et al. U.S. Pat. No. 5,108,530 issued Apr. 28, 1992, and assigned to Bayer Aktiengesellschaft, relates to a method of producing a deep drawn plastic piece in which a sheet of synthetic resin material is provided with a image-defining coating, and the image section of the sheet is preheated and then deep drawn under air pressure of more than 20 bars and preferably about 200 bars.

[0010] Raney et al. U.S. Pat. No. 4,555,968 issued Dec. 3, 1985, and assigned to Preco Industries, Inc., relates to web-fed die cutting presses having an automatic three axis die registration system. In the '968 patent, a movable die element of the die set may be shifted after an image-bearing section fo the web is moved into position in the die set to register the die element with indicia on the web along X (longitudinal), Y (transverse) and θ (rotational) axes.

[0011] Raney U.S. Pat. No. 4,697,485 issued Oct. 6, 1987 and assigned to Preco Industries, Inc., relates to a die press of the type illustrated in the '968 patent and which has a three axis (X, Y, θ) registration system which is operable to register a movable die element of the die set with an image bearing section of the web as the material is advanced into position in the die set.

SUMMARY OF THE INVENTION

[0012] The film insert forming apparatus and method for selective preheating of solid phase pressure formed web or sheet material of this invention is especially useful for deep drawing of relatively thin sheet or web material that may or may not have an image or printed characters on one surface thereof. The preheating apparatus is positioned adjacent a forming die set assembly presenting a forming station and adapted to be mounted in a hydraulically actuated press. The forming die set assembly includes a forming die set unit having a forming cavity receiving a forming die and an overlying high pressure chamber die set unit aligned therewith. The forming die set unit has a movable stripper frame in surrounding relationship to the forming die. The high pressure chamber die set unit is movable downwardly from an upper open position separated from the stripper frame to a closed position clamping material to be formed between the high pressure chamber die set unit and the stripper frame of the forming die set unit. Continued downward movement of the high pressure chamber die set unit causes the stripper frame to be shifted therewith in the same direction. Upon introduction of high pressure fluid into the high pressure chamber die set unit while the material remains clamped between the high pressure chamber die set unit and the stripper frame causes the material to be pressure formed against the forming die.

[0013] A material preheating station is provided outside of but generally proximal to the die forming cavity of the die forming unit. The preheating station includes duckbill or clamshell type preheating devices each having a heated planar plate that is in heat transfer contact with a respective adjacent surface of material at the preheating station. An upper preheating device is connected to the high pressure chamber die set unit and moves with that die set unit while a lower preheating device is connected to the stripper frame of the forming die set unit for movement with the stripper frame. When the high pressure chamber die set unit is moved upwardly relative to the forming die set unit to provide a vertical space therebetween for receipt of material to be formed, the upper preheating device shifts with and in timed relationship to the high pressure chamber die set.

[0014] Upon downward movement of the high pressure chamber die set unit into a position clamping material to be formed between the high pressure chamber die set unit and the stripper frame, the heated plate of the upper preheating device is brought into heat transfer contact with the uppermost surface of material at the preheating station. At the same time, the spatial relationship of the upper and lower preheating devices is such that the plate of the lower preheating device is in contact heat transfer relationship with the lowermost surface of the material at the preheating station. Heat transfer contact is maintained between the heated plates of the upper and lower preheating devices with respective upper and lower surfaces of the material at the preheating station by virtue of the fact that the lower preheating device is connected to and moves downwardly in timed relationship with the stripper frame as a result of downward movement of the stripper frame with the high pressure chamber die set unit.

[0015] It therefore can be seen that direct coupling of the upper and lower preheating devices of the preheating station to the high pressure chamber die set unit and the stripper frame of the forming die set unit respectively causes the upper preheating device to be moved in timed relationship to opening and closing of the high pressure die set unit without the necessity of providing extraneous timing mechanism for that purpose. Furthermore, direct connection of the lower preheating device to the stripper frame of the forming die set unit causes the lower preheating device to move in timed relationship with movement of the stripper frame.

[0016] Accordingly, upon raising of the high pressure chamber die set unit of the die set assembly to present a vertical space between the high pressure chamber die set unit and the stripper frame of the forming die set unit and conjoint upward movement of the upper preheating device leaving a vertical space between the heating plates of the upper and lower preheating devices, material to be formed may be shifted into the forming station of the die set assembly at the same time that material to be preheated is moved into the preheating station. Closing of the die set assembly by downward movement of the high pressure chamber die set unit which clamps the material to be formed between the high pressure chamber die set unit and the stripper frame also closed the preheating devices so that the heated plates thereof are in contact heat transfer engagement with opposed surfaces of the material at the material preheating station.

[0017] Further downward movement of the high pressure chamber die set unit to force the stripper frame of the forming die set unit downwardly to bring the material at the forming station into direct overlying relationship to the forming die of the forming die set unit does not result in a space being created between the heated plates of the preheating devices because of the direct connection of the upper and lower preheating devices to the high pressure chamber die set unit and the stripper frame whereby during that phase of the die set assembly forming operation, the preheating devices move downwardly in unison along with the high pressure chamber die set unit and the forming die set unit.

[0018] Contact preheating of material to be formed outside of but directly adjacent the forming cavity of the die forming unit set assembly has important advantages. Introducing heat into both sides of the material simultaneously significantly reduces time required to raise the temperature of the material to desired predetermined level. Contact heating is also more efficient both from an energy utilization standpoint as well as the time necessary to preheat the material to a prescribed temperature. Location of the preheating devices directly adjacent and preferably abutting the die set assembly reduces the distance the preheated material must travel from the preheat station to the forming station within the die set assembly, thus limiting the tendency of the preheated material to cool off to an undesired extent before the material is subjected to the pressure forming operation at the forming station.

[0019] Efficient preheating time intervals and minimum material transfer time of material from the preheating station to the forming station not only permits faster forming cycle times, but also permits closer control over the quality of the formed parts with minimum overall equipment requirements.

[0020] In a preferred embodiment of the invention the preheating devices are provided with opposed, aligned heat insulating zones of predetermined shape which cooperate to prevent the portion of material contacted by the heated plates of the preheating devices from being heated to as high a temperature as the material out of alignment with the insulating zones. The heat insulating zones are shaped to conform with certain portions of the forming die. Each insulating zone comprises an open groove in a respective heated plate of the upper and lower preheating devices with the grooves being in direct opposed alignment.

[0021] During solid phase high pressure forming of material such as synthetic resin film against a male or female forming die, the material tends to become thinner at corner edges of the forming die as compared with remaining areas of the material. This undesirable thinning of the material at areas of the die which exert more focused pressure on the material than other portions of the material, can be ameliorated by selective preheating of the material before forming. Those areas of the material that will be subjected to greater forming forces than other areas are preferably preheated to a somewhat lower preheat temperature. During forming, the material of the areas that are selectively heated to a lesser temperature than other areas tends to more readily flow during forming to minimize thinning of those areas compared with the overall material thickness of the formed part.

[0022] In order to better protect portions of the material being formed which would be unduly thinned as a result of corner pressure or the like exerted on the material by certain parts such as corners of the forming die, the areas to be protected are selectively preheated to a lower temperature than the remaining areas of the material. Selective preheating of material is therefore accomplished by providing aligned air insulating grooves in the opposed outer surfaces of the heated plates of the preheating devices. The grooves are configured to conform with the areas of the material that are to be heated to a lesser temperature than other areas of the material. The depth and width of the grooves is dependent upon the amount of air insulation required to accomplish predetermined reduced preheating of selected areas of the material.

[0023] Air insulating grooves are provided in the material contacting faces of opposed plates of the preheating devices which substantially conform in shape to the areas of the material that align with corner or other high force portions of the mold. Exemplary in this respect is a part to be formed that is of generally rectangular shape with round corners. When a preheated synthetic resin film is solid phase formed under high pressure against a male mold, the material tends to thin out around the perimeter of the rectangular mold. In order to prevent undesirable thinning of the film along the border of the generally rectangular mold, it is desirable that the areas of the film which directly overlie the corner or border of the mold during the forming process not be heated to a temperature as high as other areas of the material. The air insulating grooves in this example are therefore of an overall shape that conforms to the corner or high force generating parts of the mold.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is perspective view of film insert forming press apparatus for high pressure, solid phase forming of relatively thin web or sheet material in accordance with a preferred embodiment of the invention;

[0025]FIG. 2 is a side elevational view of the film insert forming press apparatus as illustrated in FIG. 1 and showing in-feed roll and out-feed assemblies for directing material to be formed sequentially through a preheat station and then a forming station within the press;

[0026]FIG. 3 is a plan view of the apparatus as shown in FIG. 2;

[0027]FIG. 4 is an enlarged fragmentary perspective view of clamshell type preheating devices making up the preheating station of the press apparatus;

[0028]FIG. 5 is an enlarged fragmentary end elevational view of the die set assembly and associated preheating devices forming a part of the overall press apparatus;

[0029]FIG. 6 is a horizontal cross-sectional view taken substantially on the broken line 6-6 of FIG. 5 and looking upwardly in the direction of the arrows;

[0030]FIG. 7 is a horizontal cross-sectional view taken substantially on the broken line 7-7 of FIG. 5 and looking downwardly in the direction of the arrows;

[0031]FIG. 8 is a fragmentary enlarged vertical cross-sectional view through an upper part of the press apparatus, and illustrating the high pressure chamber die set unit of the die set assembly in its open position;

[0032]FIG. 9 is a fragmentary enlarged vertical cross-sectional view similar to but at a 90° angle with respect to the illustration in FIG. 8, and also showing the high pressure chamber die set unit of the die set assembly in its open position;

[0033]FIG. 10 is a fragmentary enlarged vertical cross-sectional view similar to FIG. 9 and showing the high pressure chamber die set unit in a lowered position clamping material to be formed between the high pressure chamber die set unit and a stripper frame located in surrounding relationship to a forming die;

[0034]FIG. 11 is a fragmentary enlarged vertical cross-sectional view similar to FIG. 10 illustrating the high pressure chamber die set unit at the lower end of its path of travel in which the stripper frame has also been moved downwardly by the high pressure chamber die set unit, and the material has been deep drawn over a stationary three-dimensional mold; and

[0035]FIG. 12 is an alternate embodiment of the apparatus of this invention in which an automatic sheet feeder is provided for feeding sheets rather than a web to the press.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0036] Film insert forming apparatus 20 for high pressure, solid phase forming of relatively thin web material is illustrated in the drawings and especially in the overall showing of FIG. 1. The apparatus of this invention is especially useful as an improved adaptation of hydraulically actuated ram and platen die stamping and embossing presses. Presses of this type are illustrated and described in Preco Industries, Inc.'s U.S. Pat. No. 5,212,647 which is fully incorporated herein by specific reference thereto.

[0037] As depicted in FIGS. 1-2, and 8-12 and similar to the press of the '647 patent, apparatus 20 includes a floating bolster 22 mounted on a base 24 of the press apparatus 20 and which supports a master die set assembly broadly designated 26. Die set assembly 26 includes an upper high fluid pressure chamber die set unit 28 and an opposed lower forming die set unit 30 which is provided with a centrally located forming die 32 surrounded by a vertically shiftable stripper frame assembly 34. The die set assembly 26, which is supported by and rests on bolster 22 rotates and shifts with bolster 22 as the position of the latter is adjusted by power operators as described hereinafter. The pressure chamber die set unit 28 of master die set assembly 26 includes an upper horizontal punch plate 36 which is positioned immediately below a vertically shiftable ram block 38 forming a part of the hydraulic press. Shiftable ram block 38 is vertically reciprocal on four guides 40 by the piston 42 of hydraulic ram assembly 44. A fluid manifold plate 46 is mounted immediately below and connected to the operating ram block 38 of press 20. A pressure bell member 48 is secured to the underside of the fluid manifold plate 46. As is most evident from FIGS. 8-11, fluid manifold plate 46 has a central vertical passage 50 which receives a stationary piston 52 connected to plate 36. The passage 50 is in direct communication with the upper face of pressure bell 48.

[0038] Plate 46 is also provided with horizontal, vertically spaced fluid passages 54 and 56 that communicate with the vertical passage 50. An L-shaped high pressure fluid passage 58 has a horizontal leg extending to the center of member 48 and a downwardly extending leg opening to the underside of bell member 48 inside of the integral, depending annular rim 60 of member 48.

[0039] The stripper frame assembly 34 of lower forming die set unit 30 includes a generally rectangular horizontal main stripper frame 62 (FIGS. 6, 7 and 8-11) which defines a central forming cavity 154 that surrounds forming die 32, a removable and replaceable secondary stripper insert frame 64 spans the distance between leg portions 62 a and 62 b of main stripper frame 62. The secondary frame 64 is adapted to be constructed and configured such that the central opening 66 therein conforms to and is substantially contiguous with the perimeter of forming die 32. It is to be appreciated in this respect that in most instances a separate and distinct secondary stripper frame 64 will be provided for each individual forming die 32 such that the opening 66 will be essentially the same shape as the outer margin of the forming die 32.

[0040] As shown in FIG. 8, four vertical, horizontally spaced rods 68 each have a bolt 70 threaded into the lower end thereof which engages a respective washer 72 that underlies and provides support for the forming die set unit 30. The upper ends of rods 68 are affixed to plate 36. As a result, upward movement of ram block 38 and the plate 36 connected thereto causes the forming die set unit 30 to be lifted with ram block 38 by virtue of the support for forming die set unit 30 provided by rods 68 and associated bolts 70 and washers 72.

[0041] The horizontal block 74 of forming die set unit 30 that rests on bolster 22 carries an insulator plate 76 that supports forming die 32. Four upright, horizontally spaced headed studs 78 affixed to plate 76 and extending through main stripper frame 62 serve to limit the upward movement of stripper frame assembly 34.

[0042] Apparatus 20 is especially adapted for forming thin web material having an image imprinted thereon and in which the area to be pressure drawn and formed corresponds to or relates in a specific manner to an image or images on each sheet. Accordingly, registration of the image imprinted on each sheet is required with the forming die 32 of the forming die set unit 30 of die set assembly 26. The precision of registration may vary from job to job depending upon the nature of the image as well as the depth of the area that is to be formed in the material by the die set assembly 26. In apparatus 20 as shown in FIGS. 1-11, registration of the image of the web is accomplished by X axis adjustment of the web with respect to the forming die set unit 30 and thereby forming die 32 and by suitable Y and θ axes adjustment of the die set assembly 26 with respect to a web while a segment of the web is positioned at the forming station 80 of die set assembly 26 between high pressure chamber die set unit 28 and forming die set unit 30. In this respect, the X axis is defined by the longitudinal, horizontal in-feed path of a portion of web material 82 controlled by in-feed roll mechanism 84 and web out-feed mechanism 96 on opposite sides of the press apparatus 20. The Y axis is horizontal and perpendicular to the X axis, and θ is a vertical axis of rotation that is perpendicular to the X and Y axes.

[0043] Although not depicted in FIG. 1, it is to be recognized that the web 82 normally is provided with images and/or imprinted text or symbols which define individual, end-to-end discrete segments, each of which is to be successively directed into the forming station 80 of die set assembly 26. It therefore is necessary that the image or text on the web 82 be accurately positioned with respect to the forming die 32 at the time of pressure forming of the web material 82. In order to accomplish registration of images on the web with the forming die 32, the web 82 should be provided with registration fiducials associated with respective images or text. Sensing of the position of the images or text of a particular segment of the web 82 at the time that web segment is brought into position at forming station 80 withing die set assembly 26 is preferably accomplished with a CCD camera vision system.

[0044] “Vision system” as used herein is intended to mean a registration system as for example illustrated and described in the incorporated '647 patent. In preferred system, a pair of retractable CCD cameras 88 and 90 having associated viewing prisms are mounted on opposed upper wall surfaces of main stripper frame 62 in disposition permitting horizontal shifting of each camera and prism as a unit whereby the prisms are in overlying relationship to the web for looking down at fiducials on opposite margins of the web 82 while a segment of the web is located at forming station 80. The cameras 88 and 90 through the medium of respective prisms read the position of fiducials on web 82 and transmit digital data representative of the fiducial image positions to a control computer (not shown) for comparison with desired fiducial position data stored in the memory of the computer, all as explained in detail in the '647 patent. The CCD cameras 88 and 90 and associated prisms are retracted after the required fiducial position data has been acquired. Control signals are sent from the computer to the Y axis operator motor 92 (FIG. 8) and to the θ axis operator motor 94 (FIG. 3), as well as to in-feed roll mechanism 84 and out-feed mechanism 86 which shift the web as required for X axis registration.

[0045] Y axis adjustment of the portion of the web 82 at forming station 80 is accomplished by appropriate Y axis movement of floating bolster 22. A cross plate 96 on the frame 98 of apparatus 20 supported by the cabinet structure 100 carries a horizontal transversely extending guide 102 which slidably receives a coupling 104 that is to the composite post structure 106 to the underside of floating bolster 22. The Y axis operator motor 92 carried by and underlying plate 96 is connected to a ball screw (not shown) which is rotated by the pulley mechanism 108 connected to operator motor 92. Actuation of operator motor 92 causes the coupling 104 to slide transversely along the Y axis to move the bolster 22 and thereby die set assembly 26 which is fixed to and moveable with floating bolster 22. θ axis adjustment mechanism which includes θ axis operator motor 94 is also carried by the frame 98 and is operably coupled to floating bolster 22 as for example shown and described in the '647 patent for rotating bolster 22 in required opposite directions about the vertical axis of composite post structure 106. The time intervals of operation of motors 92 and 94 and of in-feed roll mechanism 84 and out-feed mechanism 86 is controlled by the computer of the vision system to accurately align the images on the portion of the web 82 at forming station 80 with forming die 32.

[0046] The clamshell or duckbill type preheating station 110 of apparatus 20 includes an upper preheating device broadly designated 112 and a lower preheating device 114. Viewing FIGS. 4 and 8, it can be seen that the upper preheating station 112 has a pair of upright, horizontally spaced triangular plates 116 and 118 interconnected by an upright cross plate 120. The cross plate 120 is bolted to an outer upright face of the fluid manifold plate 46 of high pressure chamber die set unit 28. Blocks 122 and 124 mounted on the inside surfaces of triangular plates 116 and 118 respectively are adjustable horizontally through the medium of horizontal slots 126. Blocks 122 and 124 are interconnected by spaced horizontal rods 128.

[0047] A horizontal cover plate 130 in spanning relationship to blocks 122 and 124 is connected to the underside of the blocks. It can be seen from FIGS. 5 and 8 that the cover plate 130 extends inwardly of the inside vertical edges of the triangular plates 116 and 118 into the space between pressure bell member 48 and the stripper frame assembly 34. A planar insulating member 132 is provided in underlying relationship to cover plate 130 and extends inwardly of die set assembly 26 to the same extent as cover plate 130 and projects outwardly from the outermost edge of cover plate 130 to an extent as shown in FIG. 4. The innermost edges of the preheating devices 112 and 114 are outside of but proximal to the die cavity 154 of stripper frame 62.

[0048] A heating layer 134 (Minco Products, Inc. Model HM6800, 0.040″ thick thermal foil being exemplary) underlies the insulating member 132 and is substantially coextensive in area therewith. In can be observed from FIG. 4 that the forwardmost margin of insulating member 132 has a series of notches 136 therein to accommodate the electrical connectors joined to foil heating layer 134. A metal plate 138, preferably formed of aluminum is situated directly beneath and in thermal transfer relationship with the foil layer 134. In a preferred embodiment of apparatus 20, the aluminum plate 138 may for example be from about ⅛th″ to ¼th″ thick with ⅛th″ being preferred. Again, the plate 138 is coextensive in area with the foil layer 134 and insulating member 132.

[0049] The lower preheating device 114 is similar in construction to preheating device 112. To that end, device 114 includes two horizontally spaced, outwardly extending L-shaped support brackets 140 (FIGS. 4 and 8) each having a relatively short inner leg 140 a and a longer outwardly projecting leg 140 b. The inner legs 140 a are bolted to an upright face of main stripper frame 62 immediately below the upper preheating device 112. A lower cover plate 142 spans the distance between legs 140 b of brackets 140 and supports a planar insulating member 144. A thermal foil layer 146 of the same material as foil layer 134, lies atop the insulating member 144 which also has notches 148 in the forward edge thereof for accommodating electrical connectors for foil layer 146. A metal plate 150, again preferably of aluminum, overlies the thermal foil layer 146. It is to be seen from FIG. 8 that the heating elements of upper heating device 112 and lower heating device 114 are coextensive in area, in direct opposition, and of the same or similar construction. The heating elements making up lower heating device 114 may also be adjusted horizontally through means of the horizontal slots 152 in legs 140 b of L-shaped brackets 140.

[0050] It is notable from viewing FIG. 8 for example that the preheating station 110 is in proximal relationship to die set assembly, and the supports for the planar heating elements each made up of a cover plate, an insulating member, thermal foil and a planar metal plate in fact rest against are connected to the high pressure chamber die set unit 28 and the forming die set unit 30. It is preferred in this respect that the distance between the lower preheating device 114 and the forming die cavity 154 defined by the main stripper frame 62 be no greater than 10× the wall thickness of frame 62, and preferably no greater than the thickness of the wall of frame 62.

[0051] In order to provide for selective heating of a segment of web 82 subjected to preheating at station 110, the outermost, directly facing surfaces 156 of plate 138 and surface 158 of plate 150 are each provided with air insulating grooves 160 and 162 respectively (FIGS. 4 and 6-8). Grooves 160 and 162 may be formed in plates 138 and 150 by conventional milling, grinding, chemical etching or equivalent metal removal processes. One especially useful technique is to place the plates 138 and 150 in a numerically controlled milling machine wherein the configuration, width and depth of grooves 160 and 162 may be carefully controlled and duplicated.

[0052] For exemplary purposes only, the grooves 160 and 162 may for example be of generally rectangular shape representative of the peripheral edge of the cover of a cell phone and therefore complemental with the outer margin 164 of forming die segments 32 a of forming die 32. Generally speaking, the grooves are from about 0.01″ to about 0.5″ deep and therefore the plates 138 and 150 are of a thickness to accommodate such grooves of desired depth. An exemplary plate in this respect my be ⅛th″ thick and provided with an insulating groove or grooves 0.05″ deep. In most instances, the insulating groove or grooves are not deeper than about ½ the thickness of respective plates 138 and 150. The width of each groove 160 and 162 is a function of the width of the area of the material that is to be preheated to a lower temperature than the preheat temperature of the remaining portion of the material.

[0053] The operating and guide structure for the die set assembly may include four fluid operated cylinders and four associated post sleeve guides. The fluid operated cylinders 166 between and at the four corners of plate 36 and block 74 are operable to open and close the press chamber die set unit and forming die set unit of die set assembly 26. The four post sleeve guides 168, two of which are between corner pairs of operating cylinders 106 serve to restrain press chamber die set unit 28 to a vertical path of travel with respect to forming die set 30.

[0054] Operation of the Preferred Embodiment

[0055] Die set assembly 26 is normally supplied as a standard part of forming apparatus 20 minus a forming die such as forming die 32 and the secondary stripper frame 64, which are fabricated by the user for each specific forming job. The only requirement in this respect is that the forming die be of a size that will fit within the forming die cavity 154. Although the die 32 illustrated in the drawings is a male die, it is to be appreciated that the die may be a male die, a female die, or a compound male and female die. The customer also fabricates the secondary frame stripper in a manner such that the central opening 66 conforms to the outer perimeter of a particular prefabricated forming die 32.

[0056] The die set assembly 26 is assembled out of the film insert forming press apparatus 20 by mounting of a forming die 32 which is configured for a particular job in the cavity 154 in disposition resting on plate 76 carried by the lowermost block 74 forming a part of the die set assembly 26. Secondary frame 64 is then bolted to main stripper frame 62.

[0057] Ram block 38 is initially moved to its upper neutral position, somewhat below its uppermost position, by retraction of piston 42 of the hydraulic ram assembly 44. The assembled die assembly 26 is inserted in the press apparatus 20 in its operating position between ram block 38 and floating bolster 22. The die assembly 26 is secured in place using conventional fasteners for that purpose. The die set assembly lifting cylinders 106 are then attached to the die set assembly 26. Next, the vision CCD camera and prism unit are attached to the stripper frame 62. The hydraulic ram piston 42 is held in its neutral raised press position with the main stripper frame 62 being suspended from plate 36 of die set assembly 26 by the four rods 68 having bolts 70 and washers 72 on the lower ends thereof which underlie the main stripper frame 62 as illustrated, for example, in FIG. 8. Block 36 of die set assembly 26 is held in its upper position by pressure applied to the bottom half of each of the four lifting cylinders 166 interposed between die assembly block 74 and upper plate 36. Fluid pressure introduced into passage 50 through line 56 exerts upward pressure on the fluid manifold plate 46 via the relieved area 170 in stationary piston 152.

[0058] Although not illustrated in FIG. 1 of the drawings it is to be understood the web 82 may be provided with a series of images or printing thereon defining parts to be pressure molded in apparatus 20. The in-feed roll mechanism 84 and associated out-feed mechanism 86 are operated to index a predetermined area of the web 82 into the forming station 80 of die set assembly 26 between high pressure chamber die set unit 28 and forming die set unit 30 of press apparatus 20 as shown in FIG. 9. The in-feed roll mechanism 84 and out-feed mechanism 86 are each operated in synchronized relationship to move a predetermined defined area of the web 82 into the forming station 80 while maintaining tension on the web.

[0059] It is also to be observed that when a predetermined area of the web 82 is shifted into the forming station 80 of die set assembly 26 as described, a similarly sized predetermined preceding area of the web is simultaneously indexed into position in preheating station 110 between the upper and lower preheating devices 112 and 114 which are in their open positions as illustrated in FIGS. 8 and 9 because the die set assembly 26 is also open. As previously described the upper preheating device 112 is attached to and moves with the upper manifold plate 46 of die set assembly 26 while the lower preheating device 114 is connected to and moves with the main stripper frame 62 of forming die set unit 30. As shown in FIGS. 8 and 9, the width of plates 138 and 150 of devices 112 and 114 in the feed direction of web 82 is preferably about equal to the cross dimension of the die assembly 26 in that same direction.

[0060] The ram assembly 44 is actuated to move piston 42 and thereby ram block 38 to its uppermost position, allowing the punch plate 36 to be moved up by the lifting cylinders 166. The uppermost position of the punch plate 36 is controlled by the four headed studs 78 attached to insulating plate 76 and thereby block 74. Movement of punch plate 36 to its uppermost position allows a small gap to develop between the ram block 38 and the upper surface of punch plate 36. This shifted position of the punch holder plate 36 causes the main stripper frame 62 to come into contact with the bottom surface of the stretch of web 82 located in forming station 80.

[0061] Next, the vision CCD camera and prism units 88 and 90 are shifted toward one another to an extent that opposed in-board prisms overlie fiducials on opposite sides of web 82 within forming station 80. Digital data from cameras 88 and 90 is transmitted to the control computer for comparison with stored data indicative of the desired accurate position of the image or printing on the stretch of web 82 in forming station 80. Depending upon the X axis difference between the stored data representative of the accurate X axis position of the image and/or printing on the stretch of web 82 at the forming station 80 and the vision observed position of such image and/or printing, the in-feed roll mechanism 84 and out-feed mechanism 86 are actuated to move the stretch of web therebetween a required amount to provide X axis compensation. Similarly, if the observed data with respect to the Y axis position of the image or printing on the web 82 is different than the stored Y axis data, operator 92 is actuated in a direction to shift the bolster 22 transversely of the web 82 in a required direction and distance. Likewise, if the observed data with respect to the θ axis position of the image or printing on the web 82 is different than the stored θ axis data, operator 94 is actuated in a direction to rotate the bolster 22 about the axis of post structure 106 in a required direction and through the necessary compensating angle. As a result of the X axis adjustment of the position of the web 82, and the Y and θ axis adjustment of the floating bolster 22, the forming die 32 is now in accurate alignment with the observed fiducials on web 82 and thereby the image or printing on web 82. The CCD camera and prism units 88 and 90 are retracted to their initial positions out of the forming station 80.

[0062] The die set assembly 26 is now in condition to be actuated for forming of the stretch of web 82 within the station that is located at forming station 80. Fluid pressure is introduced into passage 54 thus pressurizing the space withing passage 50 below stationary piston 52. Pressurization of the space below piston 52 causes the fluid manifold plate 46 and the high pressure bell member 48 to be moved downwardly thereby bringing the rim 60 of member 48 into engagement with the upper face of the stretch of web 82 therebelow and clamping the web stretch between the lower face of rim 60 of pressure bell member 48 and the secondary insert frame 64 as depicted in FIG. 10. The fluid pressure within the chamber of passage 50 below piston 52 generates sufficient clamping force to securely hold the stretch of the web 82 at forming station 80 in registered forming position throughout the forming process. A continuous O-ring provided in the lower face of rim 60 of pressure bell member 48 contacts the upper surface of the stretch of web 82 at forming station 80 to assure a pressure tight sealing surface when the pressure bell member 48 is moved into position clamping the web material between high pressure chamber die set unit 28 and stripper frame assembly 34.

[0063] In-feed roll mechanism 84 is operated to a limited extent in the web feed direction and out-feed mechanism 86 is operated in a direction opposite of the feed direction to relieve the tension on the stretch of web 82 within the die set assembly 26. The hydraulic ram of press apparatus 20 is then actuated to move ram piston 42 and thereby ram block 38 downwardly. Lowering of ram block 38 forces the assembly made up of punch plate 36, manifold plate 46 and pressure bell member 48, which is already in web clamping relationship with forming die set 30, downwardly, thereby shifting the main stripper frame 62 as well as the secondary stripper frame 64 downwardly until the stripper frames bottom out against the upper face of insulating plate 76 as shown in FIG. 11. Downward movement of the main stripper frame 62 and the secondary stripper frame 64 mounted thereon causes the stretch of the web clamped between the rim 60 of pressure bell member 48 and the stripper frame 64 to be moved downwardly in direct overlying relationship to the upwardly facing surface of forming die 32. The bolt heads of bolts 70 and associated washers 72 are allowed to move past the insulator plate 76 and block 74 so there is no interference in the clamping relationship between the rim 60 of pressure bell member 48 and the stripper frame 64 as well as main stripper frame 62. All pressure in the lifting cylinders 166 is also released so that downward movement of the main stripper frame 62 and the secondary stripper frame 64 is not impeded.

[0064] Fluid, typically heated air at about 170° F. to about 180° F., is introduced into the interior bell of member 48 via passage 58 which serves to form the web material 82 against the surface of forming die 32. The magnitude of the fluid pressure introduced into bell member 48 is a function of a number of parameters including the thickness and type of the material 82, the depth of the impression required to be formed in the material 82, the surface detail of the forming die 32 required to be reproduced in the web material 82, the temperature to which the web has been preheated as described hereinafter, the clamping force capable of being generated by the hydraulic ram assembly 44, the number of individual deep drawn cavities or protrusions which are solid phase formed in a single operation of apparatus 20, the temperature of the pressurized air introduced into bell member 48, the availability of a source of high pressure fluid of maximum desired magnitude, the cycle time chosen for the entire forming and formed part removal operation of the press apparatus 20, and other processing variables that are specific to forming of a particular part. Typical forming pressures are set forth in the above identified '530 patent and which are incorporated herein by specific reference thereto. Forming pressures in this respect may be as high as 2000 psi to 3000 psi.

[0065] The entire clamping force produced by hydraulic ram assembly 44 of forming press apparatus 20 is available to hold the maximum sized forming tool set in a closed condition during maximum pressurization of the forming cavity 154. However, the forming die cavity 154 should be sized such that the required forming pressure for the desired part multiplied by the forming surface area of the forming die 32 does not exceed the maximum clamping force produced by hydraulic ram assembly 44.

[0066] Process control software may be provided to enable the operator of forming press apparatus 20 to calculate the maximum sized forming area that can be used with the press. The operator may key in the forming area size and the desired forming pressure to be used with that specific process. If the maximum forming area with that desired pressure exceeds the capability of the press the software notifies the operator of an invalid operation. The control software also is programmed to allow the operator of press apparatus 20 to change the process parameters to adjust the solid phase forming pressure or forming die size. If there is an unexpected loss of full clamping force in the press, the control software is functional to monitor this loss of clamping force thereby stopping the forming process and notifying the operator of a process fault. Similarly, the control software also monitors the pressure of the high pressure fluid introduced into the bell chamber member 48 through passage 54 and if a loss or decrease in pressure occurs the control software again stops the process and notifies the operator of that process fault.

[0067] Relaxation of the tension on web 82 between in-feed roll mechanism 84 and out-feed mechanism 86, permits solid phase forming of the web material 82 against the surface of forming die 32 without undue thinning of the material. After completion of solid phase forming of the web material 82 against forming die 32, the fluid or air pressure in the interior of pressure bell member 48 is released. At essentially the same time, pressurized fluid is introduced into relieved area 170 of stationary piston 152 to raise the pressure chamber die set unit 28 to the position thereof illustrated in FIGS. 8 and 9.

[0068] During elevation of the punch plate 36 and the fluid manifold plate 46 as well as pressure bell member 48, the rods 68 are lifted with these components so that when the washers 72 at the lower end of rods 68 engage and move the main stripper frame 62 and secondary stripper frame 64 upwardly to the same extent as the upward movement of pressure chamber die set unit 28. The stripper frames 62 and 64 thereby serve to pull the formed portion of web 82 out of the die cavity 154 thereby stripping the formed stretch of web 82 from the forming die 32. Ram block 38 is stopped in its neutral position thus also returning punch plate 36, fluid manifold plate 46 and pressure bell member 48 to their neutral positions.

[0069] The rollers of out-feed mechanism 86 are adjustable transversely of press apparatus 20 as required so the individual rollers do not engage and adversely affect the formed surface of the web 82. The press apparatus 20 is now ready to form another part. Actuation of in-feed roll mechanism 84 and out-feed mechanism 86 serves to remove the formed stretch of web 82 from forming station 80 and to bring the preheated stretch of the web 82 into the forming station 80 at the same time a following stretch of web 82 is indexed into the preheating station 110.

[0070] Preheating station 110 forms an important and unique part of press apparatus 20. When the pressure die set unit 28 made up of punch plate 36, fluid manifold plate 46 and pressure bell member 48 are in the neutral positions thereof as illustrated in FIGS. 8 and 9, the space between plate 138 of preheating device 112 and plate 150 of preheating device 114 defines the fore and aft and side-to-side limits of material preheating station 110.

[0071] Lowering of fluid manifold plate 46 as described to bring the rim 60 of pressure bell member 48 into disposition clamping a stretch of the web material 82 between pressure chamber die set unit 28 and forming die set unit 30 as shown in FIG. 10 serves to also lower web preheating device 112 as a result of the direct connection of preheating device 112 to fluid manifold plate 46. During lowering of preheating device 112 the plate 138 of preheating device 112 first contacts the upper surface of a stretch of web material 82, and then forces that portion of the web 82 down into contacting engagement with plate 150 of preheating device. Continued downward movement of the pressure chamber die set unit 28 which also causes the stripper frame assembly 34 to be moved downwardly herewith, results in contact force being maintained on the web material in preheating station 110 by virtue of the fact the lower preheating device 114 is directly connected to main stripper frame 62 for movement therewith.

[0072] As previously described, preheating device 112 is provided with a thermal heating foil layer 134 positioned against metal plate 138 while preheating device 114 has a thermal heating foil layer 146 laying against metal plate 150. During operation of press apparatus 20, electrical current is furnished to layers 134 and 146 at a level and for time intervals to maintain plates 138 and 150 at a predetermined temperature. Accordingly, the stretch of web 82 clamped between plates 138 and 150 at preheating station 110 is subjected to heat from both of the plates 138 and 150 to preheat the web material 82 to a desired, predetermined temperature. As indicated above, the temperature to which the web 82 is preheated should not in most instances exceed T_(G).

[0073] Selected areas of the web material 82 at preheating station 110 may be insulated from being heated to as high a temperature as other areas of the web material at station 110. In order to accomplish this selective preheating, grooves 160 may be provided in the surface 156 of plate 138 and corresponding grooves 162 may be provided in the surface of 158 of plate 150. Although it is preferred that grooves 160 and 162 be open for the insulation properties of air contained in the grooves, in the alternative, the groove 160 and 162 may be partially or completely filled with a suitable solid or foam insulating material.

[0074] Typical preheat temperatures for web material 82 are also described in the referenced '530 patent and which is incorporated herein by specific reference thereto. For example, polycarbonate material having a thickness of from about 0.005″ to 0.020″ may be preheated to a temperature of from about 130° F. to about 240° F. However, those areas of the web material 82 aligned with grooves 160 and 162 do not reach the same temperature level as the remaining area of web material 82 because of the insulating affect of air or insulating material in grooves 160 and 162. The temperature differential between areas that are selectively insulated depends upon a number of factors including the compositional nature and thickness of the web material 82, the temperature of plates 138 and 150, the cross sectional areas of grooves 160 and 162, whether air or a solid insulating medium is relied upon in grooves 160 and 162, the length of time of the preheating cycle, and other similar factors.

[0075] The principal goal of selective preheating of the web 82 at preheating station 110 by providing insulation for certain defined areas of the web is to improve the physical properties of the part formed in forming station 80. In particular, where the material 82 is formed over a forming die having corner margins or other surface characteristics which tend to impose greater forces on the material 82 as compared with other less focused force areas, the material tends to become thinner at those areas of higher force and can actually result in separation of the material along lines where higher forces are imposed. By preheating the material 82 to a lower temperature at the areas of the material which is formed over corners, margins or high force creating surfaces of the forming die 92, the material tends to flow more uniformly at the high force areas with less tendency to become thinner than the remainder of the formed material at the high force zones.

[0076] In the representative formed part illustrated in the drawings comprising a cover for a cell phone, the outer perimeter of the formed area is solid phase pressure formed to a greater depth than the central portion of the cell phone part. By providing insulation through the means of opposed, aligned grooves 160 and 162 which are configured to conform to the outer perimeter of the cell phone cover defining forming die 32, the areas of the web 82 which are formed over the perimeter margin of each cell phone cover defining forming die are not preheated to as high a temperature as the remaining preheated areas of web 82. The result is the web material 82 deep drawn over the corner areas of the cell phone cover forming die flows more readily and does not have as great a tendency to become thinner as would otherwise be the case.

[0077] Positioning of the preheating station 110 in close abutting relationship to the stripper frame 62 minimizes the material wasted during the forming process in that a maximum amount of each stretch of web material 82 is successively indexed to the preheating 110 and then to the forming station 80. The only material that is necessarily wasted is limited to the thickness of the wall of the stripper frame 62.

[0078] Alternate Embodiment of the Invention

[0079] The film insert forming press apparatus 220 illustrated in FIG. 12 of the drawing is identical to press apparatus 20. However, in this case, a conventional automatic sheet feeder 222 is provided for sequentially delivering individual sheets of material to be formed to the preheat station 210 and to then shift the preheated sheet into the forming station 280 of the die set assembly 226. Operation of the press 220 is the same as the operation of the press apparatus 20 previously described in that sheets are sequentially fed to the preheating station then to the forming station, and finally removed as formed sheets from the forming die assembly of the press. This stripping process is repeated until completion of the job. 

1. In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof; a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of opposed material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition, at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof, each device provided with a material heating element having a heat insulating zone of predetermined shape which prevents the portion of material engaged by the devices at the preheating station that is in general alignment with the insulating zone from being heated to as high a temperature as the material out of alignment with the insulating zone; and structure opening and closing the preheating devices at the preheating station in timed relationship to opening and closing of the die set units to effect preheating of material as other material is pressure formed in the die set assembly.
 2. Apparatus as set forth in claim 1, wherein each device provided with a material heating element has a heat insulating zone shaped to conform with certain portions of the forming die.
 3. Apparatus as set forth in claim 1, wherein each device provided with a heating element has an open insulating zone defining groove in the surface of the element that engages the material when the material is at said material preheating station.
 4. Apparatus as set forth in claim 1, wherein each device provided with a heating element has an insulating zone defining groove in the surface of the element that engages the material when the material is at said material preheating station, and insulating material at least partially filling said groove.
 5. Apparatus as set forth in claim 3, wherein each of the devices is provided with an open insulating zone defining groove in the surface of each of the elements that engages the material when the material is at said material preheating station.
 6. Apparatus as set forth in claim 5, wherein the open insulating zone defining groove in each preheating devices is aligned with the open insulating zone defining groove in the opposed preheating device.
 7. Apparatus as set forth in claim 5, wherein said insulating zone defining grooves are configured to generally conform to the perimeter of the forming die.
 8. Apparatus as set forth in claim 5, wherein said insulating zone defining grooves are each of a depth approximately 5× the thickness of the material.
 9. Apparatus as set forth in claim 5, wherein said insulating zone defining groove is configured to generally conform to the perimeter of the forming die.
 10. Apparatus as set forth in claim 1, wherein said structure includes components for connecting said at least one movable device to the high pressure die set unit so that said at least one movable device moves with the high pressure die set unit in timed relationship therewith.
 11. Apparatus as set forth in claim 1, wherein each of said pair of preheating devices is provided with a material heating element.
 12. Apparatus as set forth in claim 5, wherein each of said preheating devices includes a generally planar plate engageable with a respective opposed surface of material at the heating station.
 13. Apparatus as set forth in claim 12, wherein the insulating zone defining grooves in the plates are of a depth from about 0.01″ to about 0.50″.
 14. Apparatus as set forth in claim 12, wherein the insulating zone defining grooves in the plates are of a depth of about ½ the thickness of a respective plate.
 15. Apparatus as set forth in claim 12, wherein each of said material heating elements is a resistance heating member extending across a substantial portion of the area of each of the plates.
 16. Apparatus as set forth in claim 1, wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition ranging from a position abutting the die set assembly to a position no more than about 10× the thickness of said wall of the die set assembly frame member.
 17. Apparatus as set forth in claim 1, wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition ranging from a position abutting the die set assembly to a position no more than about 5× the thickness of said wall of the die set assembly frame member.
 18. Apparatus as set forth in claim 1, wherein said forming die set unit includes a frame member having a wall of predetermined cross-sectional thickness and disposed in generally surrounding relationship to the forming die, the devices of said material preheating station being located in disposition generally abutting the die set assembly.
 19. Apparatus as set forth in claim 1, wherein the forming die set unit has a frame in generally surrounding relationship to the forming die and wherein the frame of the forming die set unit and the high pressure die set unit both move unitarily after the material is clamped between the frame of the forming die set unit and the high pressure chamber die set unit, said structure including components for joining one of the preheating devices with the high pressure chamber die set for movement therewith, and said structure further including components for joining the other of the preheating devices with the frame of the forming die set unit for movement of said other preheating device with said frame of the forming die set unit.
 20. Apparatus as set forth in claim 1 for forming material having die registration fiducials and wherein is included a movable bolster supporting the die set assembly for movement with the bolster, and die set assembly registration components for shifting the bolster to move the die set assembly into register with fiducials on the material prior to forming of material within the die set assembly.
 21. Apparatus as set forth in claim 1 for forming material in web form and wherein is included in-feed and out-feed rollers on opposite sides of the die set assembly engageable with the web for sequentially moving selected areas of the web material into said preheating station when the die set units are in said first spaced positions thereof.
 22. Apparatus as set forth in claim 1 for forming sheet material and wherein is included a sheet feeder for sequentially moving each sheet into the material preheating station and then into the die set unit assembly when the die set units are in said first spaced positions.
 23. In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof; and a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of clamshell defining material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition, at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof, each device provided with a material heating element having an air insulating zone of predetermined shape which prevents the portion of material engaged by the devices at the preheating station that is in general alignment with the insulating zone from being heated to as high a temperature as the material out of alignment with the insulating zone.
 24. In apparatus for high pressure, solid phase forming of relatively thin material having opposed surfaces, said apparatus including a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said apparatus comprising: mechanism operable to receive material to be formed and to direct the material to the forming station of the die set assembly when the die set units are in said first positions thereof; and a material preheating station outside of but generally proximal to the forming cavity of the forming die set unit, said preheating station being provided with a pair of clamshell defining material engaging preheating devices, at least one of said devices being movable relative to the other device with the devices receiving material clamped therebetween when the devices are in first spaced disposition and engaging opposed surfaces of the material when the devices are in second closed material preheating disposition, at least one of the devices being provided with a material heating element for preheating material at the preheating station when the devices are in said second preheating disposition thereof.
 25. Apparatus as set forth in claim 22, wherein each of the devices is provided with a material heating element.
 26. Apparatus as set forth in claim 22, wherein is provided structure opening and closing the preheating devices at the preheating station in timed relationship to opening and closing of the die set units to effect preheating of material as other material is pressure formed in the die set assembly.
 27. A method for high pressure, solid phase forming of relatively thin material having opposed surfaces in apparatus which includes a die set assembly presenting a material forming station and provided with a forming die set unit having a forming cavity which receives a forming die and an opposed high pressure chamber die set unit, at least one of said die set units being movable with respect to the other die set unit, said die set units receiving material therebetween when the die set units are in first spaced positions and functional to clamp the material therebetween when the die set units are in second closed forming positions for solid phase forming of the material against the forming die upon introduction of high pressure fluid into the chamber die set unit, said method comprising the steps of: preheating material at a preheating station outside of but generally proximal to the forming die cavity of the forming die set unit; providing at least one air insulation zone at the preheating station to prevent areas of the material at the preheating station generally aligned with the insulation zone from being heated to as high a temperature as the material out of alignment with the insulating zone; and successively shifting material to the preheating station and then to the forming station of the die set assembly after preheating of the material.
 28. A method as set forth in claim 25, wherein is included the step of applying heat to opposite sides of material at said preheating station.
 29. A method as set forth in claim 25, wherein is included the step of preheating material at the preheating station at generally the same time previously preheated material is formed in the forming station of the die set assembly.
 30. A method as set forth in claim 25, wherein is included the step of providing an air insulation zone on opposite sides of material at the preheating station.
 31. A method as set forth in claim 28, wherein is included the step of providing air insulation zones on opposite sides of material at the preheating station each of a shape correlated with the shape of the forming die. 